Radiation patterning tools are utilized during semiconductor processing to pattern radiation (such as, for example, ultraviolet light). The patterned radiation is projected against a radiation-imageable material (such as, for example, photoresist) and utilized to create a pattern in the radiation-imageable material. The utilization of patterned radiation for forming a desired pattern in a radiation-imageable material is typically referred to as photolithography. The radiation-patterning tools can be referred to as photomasks or reticles. The term “photomask” is traditionally understood to refer to masks which define a pattern for an entirety of a wafer, and the term “reticle” is traditionally understood to refer to a patterning tool which defines a pattern for only a portion of a wafer. However, the terms “photomask” (or more generally “mask”) and “reticle” are frequently used interchangeably in modern parlance, so that either term can refer to a radiation-patterning tool that encompasses either a portion or an entirety of a wafer. For purposes of interpreting this disclosure and the claims that follow, the term “reticle” is utilized to generally refer to any radiation-patterning tool, regardless of whether the tool is utilized to pattern an entirety of a substrate or only a portion of the substrate.
An exemplary reticle 10 is illustrated in FIG. 1. The reticle comprises a substrate 12, and patterned layers 14 and 16 supported by the substrate. The substrate 12 is relatively transparent to radiation which is ultimately to be patterned by reticle 10, as compared to the material 14 which is relatively opaque to such radiation. The term “relatively” is utilized throughout this document to indicate that a material has a particular quantitative property relative to another. For instance, the term “relatively opaque” is utilized to indicate that a material is more opaque than another material, with such other material being referred to as being “relatively transparent”. Also the term “relatively high refractive index” is utilized to indicate that a material has a higher refractive index than another material, with such other material being referred to as having a relatively low refractive index.
Typically, substrate 12 will comprise, consist essentially of, or consist of quartz; and material 14 will comprise, consist essentially of, or consist of chromium.
Openings 18 extend through the patterned layers 14 and 16. In operation, radiation is passed through substrate 12 and toward the layers 14 and 16. Such radiation is blocked by material 14, but passes through the windows 18. Accordingly, the radiation adopts a pattern upon passing through the reticle 10.
The radiation which is passed through reticle 10 can be back-reflected off of various surfaces beneath the reticle, and accordingly material 16 is provided in an attempt to preclude such back-reflected radiation from entering reticle 10. Material 16 will typically comprise, consist essentially of, or consist of chromium oxide or chromium oxynitride.
FIG. 2 shows the reticle 10 in operation. The reticle is shown above a lens 20, which in turn is above a semiconductor construction 22 comprising a radiation-imageable material 24.
Radiation (represented by arrows 26) passes downwardly through reticle 10 and is patterned by the combined opaque material 14 and windows 18 extending through the opaque material. The patterned radiation passes through focusing lens 20, and then to radiation-imageable material 24.
A problem that can occur during utilization of the reticle is that a fraction of the incident radiation can be reflected from interfaces of a quartz-containing substrate 12 and chrome-containing material 14 (so-called quartz/chrome interfaces), and travel within the substrate 12 to cause various problems, as discussed in more detail below with reference to FIG. 5. The reflected radiation is represented by arrows 28 in FIG. 2. Another problem that can occur is that some radiation can be reflected from a surface of the lens and back toward reticle 10 and not be blocked by material 16. The back-reflected radiation can then enter substrate 12 and cause various problems.
The reticle 10 of FIGS. 1 and 2 is commonly referred to as a binary mask structure. Other types of reticles are known in the art, and also commonly utilized. FIGS. 3 and 4 illustrate an embedded attenuated phase shifting mask reticle structure 30 and a bi-layer reticle structure 40, respectively. In referring to FIGS. 3 and 4, similar numbering will be utilized as was used above in describing FIG. 1, where appropriate. The reticle structure 30 of FIG. 3 comprises the substrate 12 described above with reference to FIG. 1. Construction 30 differs from the construction 10 of FIG. 1 in that the construction 30 comprises a radiation-phasing layer 32. The layers 14 and 16 (FIG. 1) may initially be present during patterning of layer 32, but will typically be removed from at least the primary patterned area of a reticle comprising the phasing material. The primary patterned area of a reticle is the portion of the reticle containing a pattern which is to be used in photolithographically patterning a photosensitive material. Other portions of the reticle can be referred to as boundary regions. Such other portions can be patterned with, for example, alignment markings, but are not generally used to pattern light during photolithography. It is common for the layers 14 and 16 to remain over the boundary region.
Phasing material 32 can comprise numerous compositions known in the art, and in typical aspects will comprise MowSixOyNz, where w, x, y and z are numbers greater than zero. The openings 18 typically extend through phasing material 32, as shown.
The reticle structure 40 of FIG. 4 also comprises the substrate 12 discussed previously with reference to FIG. 1. Additionally, the structure 40 comprises a radiation-attenuating layer 42 and a final shifting layer 44. The radiation-attenuating layer 42 will typically comprise, consist essentially of, or consist of tantalum, and the shifting layer 44 will typically comprise, consist essentially of, or consist of silicon dioxide. In some aspects, the radiation-attenuating layer can comprise, consist essentially of, or consist of hafnium-doped tantalum; and in some aspects the shifting layer can comprise, consist essentially of, or consist of nitrogen-doped silicon dioxide. The openings 18 will typically extend through radiation-attenuating layer 42 and shifting layer 44, as shown. The layers 14 and 16 (FIG. 1) may initially be present during patterning of one or both of layers 42 and 44, but will typically be removed from at least the primary patterned area of a reticle comprising the layers 42 and 44.
Various problems can exist with all of the prior art reticles described with reference to FIGS. 1, 3 and 4, and with other types of reticles, due to light reflected from quartz/chrome interfaces or other interfaces, and/or due to back-reflected light entering the reticles. It would be desirable to alleviate such problems.